import {
  createInitialInitiativeState,
  initiativeManualLetter,
  initiativeNpcEntryId,
  initiativePlayerEntryId,
  isInitiativeConditionId,
  newInitiativeManualId,
  pickInitiativeManualGradient,
  type InitiativeEntry,
  type InitiativeEvent,
  type InitiativePresenceNpc,
  type InitiativePresencePlayer,
  type InitiativeState,
} from '../../shared/types/initiative';

function withoutId(ids: readonly string[], id: string): string[] {
  return ids.filter((x) => x !== id);
}

function ensureActiveValid(state: InitiativeState): InitiativeState {
  if (state.activeId != null && state.order.includes(state.activeId)) return state;
  const nextActive = state.order[0] ?? null;
  if (state.activeId === nextActive) return state;
  return { ...state, activeId: nextActive };
}

export class InitiativeSessionStore {
  private state: InitiativeState = createInitialInitiativeState();

  getState(): InitiativeState {
    return this.state;
  }

  clear(): InitiativeState {
    const enabled = this.state.enabled;
    this.state = { ...createInitialInitiativeState(), enabled, revision: this.state.revision + 1 };
    return this.state;
  }

  dispatch(event: InitiativeEvent): InitiativeState {
    switch (event.kind) {
      case 'clear': {
        this.state = {
          ...createInitialInitiativeState(),
          enabled: this.state.enabled,
          revision: this.state.revision + 1,
        };
        return this.state;
      }
      case 'setEnabled': {
        if (this.state.enabled === event.enabled) return this.state;
        this.state = {
          ...this.state,
          revision: this.state.revision + 1,
          enabled: event.enabled,
        };
        return this.state;
      }
      case 'syncPresence': {
        return this.syncPresence(event.npcs, event.players, event.playersVisible);
      }
      case 'reorder': {
        const allowed = new Set(this.state.order);
        const nextOrder = event.order.filter((id) => allowed.has(id));
        for (const id of this.state.order) {
          if (!nextOrder.includes(id)) nextOrder.push(id);
        }
        if (nextOrder.length === this.state.order.length && nextOrder.every((id, i) => id === this.state.order[i])) {
          return this.state;
        }
        this.state = ensureActiveValid({
          ...this.state,
          revision: this.state.revision + 1,
          order: nextOrder,
        });
        return this.state;
      }
      case 'setActive': {
        if (event.id != null && !this.state.order.includes(event.id)) return this.state;
        if (this.state.activeId === event.id) return this.state;
        this.state = {
          ...this.state,
          revision: this.state.revision + 1,
          activeId: event.id,
        };
        return this.state;
      }
      case 'next': {
        if (this.state.order.length === 0) {
          if (this.state.activeId == null) return this.state;
          this.state = { ...this.state, revision: this.state.revision + 1, activeId: null };
          return this.state;
        }
        const cur = this.state.activeId ? this.state.order.indexOf(this.state.activeId) : -1;
        const nextIdx = cur < 0 ? 0 : (cur + 1) % this.state.order.length;
        const nextId = this.state.order[nextIdx] ?? null;
        if (nextId === this.state.activeId) return this.state;
        this.state = {
          ...this.state,
          revision: this.state.revision + 1,
          activeId: nextId,
        };
        return this.state;
      }
      case 'addManual': {
        const name = event.name.trim();
        if (!name) return this.state;
        const id = newInitiativeManualId();
        const entry: InitiativeEntry = {
          id,
          kind: 'manual',
          name,
          letter: initiativeManualLetter(name),
          gradient: pickInitiativeManualGradient(),
        };
        this.state = {
          ...this.state,
          revision: this.state.revision + 1,
          entries: { ...this.state.entries, [id]: entry },
          order: [...this.state.order, id],
          activeId: this.state.activeId ?? id,
        };
        return this.state;
      }
      case 'moveToReserve': {
        if (!this.state.order.includes(event.id)) return this.state;
        if (!this.state.entries[event.id]) return this.state;
        const order = withoutId(this.state.order, event.id);
        const reserve = this.state.reserve.includes(event.id)
          ? this.state.reserve
          : [...this.state.reserve, event.id];
        this.state = ensureActiveValid({
          ...this.state,
          revision: this.state.revision + 1,
          order,
          reserve,
        });
        return this.state;
      }
      case 'restoreFromReserve': {
        if (!this.state.reserve.includes(event.id)) return this.state;
        if (!this.state.entries[event.id]) return this.state;
        const reserve = withoutId(this.state.reserve, event.id);
        const order = this.state.order.includes(event.id)
          ? this.state.order
          : [...this.state.order, event.id];
        this.state = {
          ...this.state,
          revision: this.state.revision + 1,
          order,
          reserve,
          activeId: this.state.activeId ?? event.id,
        };
        return this.state;
      }
      case 'deleteEntry': {
        if (!this.state.entries[event.id]) return this.state;
        const { [event.id]: _removed, ...entries } = this.state.entries;
        const { [event.id]: _c, ...conditions } = this.state.conditions;
        this.state = ensureActiveValid({
          ...this.state,
          revision: this.state.revision + 1,
          entries,
          conditions,
          order: withoutId(this.state.order, event.id),
          reserve: withoutId(this.state.reserve, event.id),
        });
        return this.state;
      }
      case 'addCondition': {
        if (!this.state.entries[event.id]) return this.state;
        if (!isInitiativeConditionId(event.conditionId)) return this.state;
        const cur = this.state.conditions[event.id] ?? [];
        if (cur.includes(event.conditionId)) return this.state;
        this.state = {
          ...this.state,
          revision: this.state.revision + 1,
          conditions: {
            ...this.state.conditions,
            [event.id]: [...cur, event.conditionId],
          },
        };
        return this.state;
      }
      case 'removeCondition': {
        const cur = this.state.conditions[event.id];
        if (!cur?.includes(event.conditionId)) return this.state;
        const next = cur.filter((c) => c !== event.conditionId);
        const conditions = { ...this.state.conditions };
        if (next.length === 0) delete conditions[event.id];
        else conditions[event.id] = next;
        this.state = {
          ...this.state,
          revision: this.state.revision + 1,
          conditions,
        };
        return this.state;
      }
      default: {
        const _exhaustive: never = event;
        return _exhaustive;
      }
    }
  }

  private syncPresence(
    npcs: readonly InitiativePresenceNpc[],
    players: readonly InitiativePresencePlayer[],
    playersVisible: boolean,
  ): InitiativeState {
    const npcByPlacement = new Map(npcs.map((n) => [n.placementId, n]));
    const playerById = new Map(players.map((p) => [p.playerId, p]));

    let entries: Record<string, InitiativeEntry> = { ...this.state.entries };
    let order = [...this.state.order];
    let reserve = [...this.state.reserve];
    let conditions = { ...this.state.conditions };
    let changed = false;

    for (const [id, entry] of Object.entries(entries)) {
      if (entry.kind === 'manual') continue;
      if (entry.kind === 'npc') {
        const live = npcByPlacement.get(entry.placementId);
        if (!live) {
          delete entries[id];
          delete conditions[id];
          order = withoutId(order, id);
          reserve = withoutId(reserve, id);
          changed = true;
          continue;
        }
        if (entry.name !== live.name || entry.avatarAssetId !== live.avatarAssetId || entry.npcId !== live.npcId) {
          entries[id] = {
            ...entry,
            npcId: live.npcId,
            name: live.name,
            avatarAssetId: live.avatarAssetId,
          };
          changed = true;
        }
        continue;
      }
      const live = playerById.get(entry.playerId);
      if (!live) {
        delete entries[id];
        delete conditions[id];
        order = withoutId(order, id);
        reserve = withoutId(reserve, id);
        changed = true;
        continue;
      }
      if (entry.name !== live.name) {
        entries[id] = { ...entry, name: live.name };
        changed = true;
      }
    }

    for (const npc of npcs) {
      const id = initiativeNpcEntryId(npc.placementId);
      if (entries[id]) continue;
      entries[id] = {
        id,
        kind: 'npc',
        placementId: npc.placementId,
        npcId: npc.npcId,
        name: npc.name,
        avatarAssetId: npc.avatarAssetId,
      };
      order.push(id);
      changed = true;
    }

    for (const player of players) {
      const id = initiativePlayerEntryId(player.playerId);
      if (entries[id]) continue;
      entries[id] = {
        id,
        kind: 'player',
        playerId: player.playerId,
        name: player.name,
      };
      order.push(id);
      changed = true;
    }

    const wasVisible = this.state.playersVisible;
    if (wasVisible && !playersVisible) {
      const playerIdsInOrder = order.filter((id) => entries[id]?.kind === 'player');
      if (playerIdsInOrder.length > 0) {
        for (const id of playerIdsInOrder) {
          order = withoutId(order, id);
          if (!reserve.includes(id)) reserve.push(id);
        }
        changed = true;
      }
    }

    if (this.state.playersVisible !== playersVisible) changed = true;

    if (!changed) {
      // Still update playersVisible if somehow same structure
      if (this.state.playersVisible === playersVisible) return this.state;
    }

    let next: InitiativeState = {
      ...this.state,
      revision: this.state.revision + 1,
      entries,
      order,
      reserve,
      conditions,
      playersVisible,
    };
    next = ensureActiveValid(next);
    this.state = next;
    return this.state;
  }

  load(next: Omit<InitiativeState, 'revision'>): InitiativeState {
    this.state = ensureActiveValid({
      ...next,
      revision: this.state.revision + 1,
      entries: { ...next.entries },
      order: [...next.order],
      reserve: [...next.reserve],
      conditions: { ...next.conditions },
    });
    return this.state;
  }
}